Process of reducing nitro compounds.



Ni'Tnn TATES PATENT heron,

HUGO GERRESIIEIM, OF COLOGNE-EHRENFELD, GERMANY,

PROCESS OF REDUClNG NITRO COMPOUNDS.

SPECIFICATION forming part of Letters Patent N 0. 691,132, dated January14, 1902.

Application filed May 16, 1901. Serial No. 60,575. (No specimens.)

T0 at whom it may concern:

Be it known that I, HUGO GERREsHEIM, a subject of the Emperor ofGermany, residing at Cologne-Ehrenfeld, Germany, have inven ted acertain new and useful Reducing Process by Means of Iron and Alkali, ofwhich the following is a specification.

Besides the old and industrially-available methods for effecting thereduction of nitro compounds and other substances related thereto bymeans of iron or tin in acid solution or by zinc-dust in alkalinesolution several other methods have also been devised. V. Dechendhastried to effect the reduction of nitro compounds by means of zinc (withor Without the addition of iron) in presence of aqueous-salt solutions.This method is described in German Patent No. 43,230, which has lapsed.Then Whol (Reports of the Proceedtngs ofthe German C'hemc'c. $00., 1894,fol. 1432) has worked with zinc or iron in neutral solution and hassucceeded in obtaining hydroxylamin derivatives by the action of zinc inthe presence of neutral salts, (German Patent No. 84,138,) and whenworking with iron in neutral solution he has even obtained smallquantities of anilin; but all these methods were not worked on amanufacturing scale, and the same holds true of the reaction for theobtainment of azo bodies by means of finelydistributed lead in alkalinesolution. (Wohl, German Patent No. 81,129,11owlapsed.) This was due inpart to the very unsatisfactory yields and then in view of these methodsbeing too expensive for practical working. The only cheap reducing agentwithin easy reach is iron.

I have found that iron and alkali in mixture possess very markedreducing properties. If this agent is applied to nitro-benzol, forinstance, I obtain thereby azoxy-benzol, azobenzol, hydrazo-benzol, andanilin, and I am also enabled to obtain any of these bodies separately.Thus I may, for instance, obtain hydrazo-benzol by the reduction ofazoxy-benzol or azo-benzol, and so on.

By using sodium hydrate, for instance, as the alkaline agent thereducing action seems to be such that the metallic iron is firstconverted into a sodium salt of the oxid of iron, which forms a thickpaste with the excess of sodium hydrate used, and from which on theaddition of Water hydroxid of iron or oxid of iron may be separated as abrown powder in a state of very fine subdivision, which is very suitablefor use as a painting material. The solution of sodium hydrate resultingafter the separation may be concentrated and used over again forreducing new quantities of material.

I may mention as a further technical ad-' vantage as compared with thereducing process by means of zinc-dust and alkali that the expensivezinc-dust is replaced by the comparatively inexpensive iron. In view ofthe lower molecular weight of the latter and in consequence of itsproperty of becoming oxidized into the oxid Fe O a considerably smallerquantity of iron is used for the reduction than in the case ofzinc-dust, which can only oxidize intoZnO.

Thus, for instance, for manufacturing hy drazo-benzol from one thousand(1,000) kilograms nitro-benzol it needs only nine hundred to onethousand (900 to 1,000) kilograms iron instead of sixteen hundred(1,600) kilograms of zinc dust, the price of which is about ten times ashigh as that of iron. Then in my invention the alkali used can berecovered, while in the process of reduction by zinc in alkalinesolution the alkali is not only lost, but requires correspondingquantities of acid for neutralization.

Example of reducing a m'tro compound into azoocy or into azo or hydrazooompozmd. One thousand kilograms nitro benzol and seven hundred andfifty kilograms of iron are put into a suitable vessel provided with anagitator and with means for heating and cooling the contents of it. Thenthe heat is raised to ninety (90) degrees centigrade. Strong sodiumhydrate in solution or a mixture of sodium-hydrate solution and of solidsodium hydrate is then added gradually, the temperature being kept atabout 100 to 110 centigrade by the admission of steam or ofcooling-wate1z After three hundred (300) kilograms of sodium hydratehave been added a further quantity of three hundred (300) kilograms ofsodium hydrate is added with seven hundred and fifty (750) kilogramsmore of iron. The reducing action first leads to the formation ofazoxy-benzol, and after the nitro compound has been used up azo-benzolis formed. Only after nearly all the azoxybenzol has been converted intoazo-benzol and the temperature of solidification of the mass has gone upto about 63 centigrade hydrazobenzol is formed. Thus the process may beinterrupted at any stage for the manufacture of azoxy-benzol or ofazo-benzol or of hyd razobenzol.

For the reduction to hydrazo-benzol the temperature may be raised sothat the hydrazo-benzol forms a molten mass and may after the reductionhas been finished (which is indicated by the liquid becoming almostcolorless) be poured off and allowed to run into molds, where itsolidifies. Theremaining paste is diluted with water. Not used upmetallic iron will then deposit and hydroxid or oxid of iron isseparated. The sodium hydrate is then evaporated for the purpose offurther reductions. The iron that has not been used up is used overagain. For each one thousand (1,000) kilograms of the nitro compoundonly from nine hundred to one thousand (900 to 1,000) kilograms of ironare used.

It is obvious that the relative proportions of sodium hydrate, of water,and of nitro compound, 850., and the temperature may be changed and maybe different from those given by way of examples.

Instead of submitting the nitro compounds, 850., alone to the reducingprocess the process may also be carried outwith nitro compounds, &c., insolution of hydrocarbons or alcohols. This is especially advisable inthe case of substances whose hydrazo compounds show a high temperatureof solidification.

What I claim, and desire to secure by Let ters Patent of the UnitedStates, is-

The process for efiecting the reduction of organic nitro compounds andof intermediate reduction products still capable of reduction whichconsists in the treatment of these substances with iron and alkali,substantially as described.

In witness whereof I have hereunto set my hand in presence of twowitnesses.

HUGO GERRESHEIM.

Witnesses:

CHARLES L. SIMPLE, KARL SoHMITT.

